Cold-case PRs

Folks!
It's around that time (over 200 PRs with some 2 years old) when we need to
consider closing some abandoned PRs. We have a lot more active maintainers
now today than we had 1 or 2 years ago, we are better able to keep up with
new PR demand, but it's still not perfect.
I've created a GitHub Label : *Potential_Cold_Case_PR.*
I've started labeling some old PRs likewise and pinging the submitters.
Anyone in the community can help with labeling and pinging submitters. If
we (maintainers) find the PR abandoned (i.e. no updates from submitters for
a few days), we can close the PRs.
Additionally, if the JIRAs themselves are obsolete and no longer apply, we
can consider closing the JIRAs as obsolete.
Here's one example :
https://github.com/apache/incubator-airflow/pulls/vijaysbhat
-s